PerScreenDpi | QLabels incorrectly handle scale for icons (#4070)

* Fixes to icon generation. Generating a pixmap out of a size won't take the screen scaling factor into account, resulting in blurry results.
Note that this is not a catchall solution, every case needs to be addressed manually.

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

* HighDpi fixes for startup splashscreen and About dialog

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

* Add helper function to generate appropriate pixmaps for a screen based on its dpi settings.

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

Code/Editor/WelcomeScreen/WelcomeScreenDialog.cpp

@@ -34,6 +34,7 @@
 // AzQtComponents
 #include <AzQtComponents/Components/Widgets/CheckBox.h>
 #include <AzQtComponents/Components/WindowDecorationWrapper.h>
+#include <AzQtComponents/Utilities/PixmapScaleUtilities.h>
 
 // Editor
 #include "Settings.h"
@@ -79,8 +80,11 @@ WelcomeScreenDialog::WelcomeScreenDialog(QWidget* pParent)
     {
         projectPreviewPath = ":/WelcomeScreenDialog/DefaultProjectImage.png";
     }
+    
     ui->activeProjectIcon->setPixmap(
-        QPixmap(projectPreviewPath).scaled(
+        AzQtComponents::ScalePixmapForScreenDpi(
+            QPixmap(projectPreviewPath),
+            screen(),
             ui->activeProjectIcon->size(),
             Qt::KeepAspectRatioByExpanding,
             Qt::SmoothTransformation